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Process Control Daemon (PCD) is an open source, light-weight system level process manager/controller for Embedded-Linux based projects (such as consumer electronics and network devices). This kind of a tool provides a complementary service for any Embedded Linux driven product and is specialized for the needs of embedded products. However, Embedded Linux distributions do not provide such a tool. Other similar tools which are available are not suited for embedded products in terms of compatibility, performance and limited hardware resources. The PCD is a proven solution that already drives millions of devices in the world. ==Background== The PCD project was designed and implemented by (Hai Shalom ), senior software engineer at Texas Instruments Israel at the time, as part of his M.Sc. degree in Computer Science. The project was initiated due to a true need in one of Texas Instruments’ broadband solutions (ARM1176 Running MV-Linux Pro-5.00). The system was originally started with shell scripts, where the init process started the ''rcS'' script, and it started some other scripts. Due to the rapid development process of the system’s software, more processes and tasks were added, and the scripts became too long, unreadable and hard to maintain. There was no efficient way to control the startup process of the system. Synchronizing inter-process dependency was difficult and determining the order of initialization required a lot of effort. For example, a daemon which listens on a socket must precede any clients that send data on this socket. With shell scripts, there is no efficient way to verify this condition. A service with a complex state machine that needs to be in a specific state before it is ready has no standard means to synchronize with its clients. Monitoring the system’s health was another issue. There was no entity that monitored and controlled the processes in the system. Therefore, in case of a crash, the system became unstable or unusable until the crashed process was manually detected. At that time, the runtime debugging capabilities were very limited. In case of a process crash, there was no debug information available, unless compiling a special version that supports low optimizations, debug symbols and a GDB server. Once PCD was integrated into the product, the final results showed reduced startup time and great improvements in the system’s robustness, reliability and availability. The Debugging and remote debugging capabilities were also improved due to the extended debug information which was available in case of a crash (Segmentation fault, bus error, or similar). The project is no longer active but has been extended to support more embedded architectures and new features. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Process control daemon」の詳細全文を読む スポンサード リンク
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